Registration Dossier

Administrative data

Description of key information

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Read-across from GLP-compliant guideline study performed with similar substance.
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
of 2010
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
of 2008 as amended 2012
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of study:
mouse local lymphnode assay (LLNA)
Test material information:
Composition 1
Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Mouse (healthy females only), strain: CBA/Ca with appropriate range of bodyweight at study start.
- Source: Charles River (UK) Ltd.
- Age at treatment start (1st induction): Eight to ten weeks.
- Weight at treatment start (1st induction): Minimum 17.9 g, maximum 21.9 g.
- Housing: Two animals per polycarbonate cage inside a barriered rodent facility.
- Bedding material: Woodflake bedding.
- Cage enrichment: Nestlets and plastic shelter
- Diet (ad libitum): Standard rodent diet (Rat and Mouse No. 1 Maintenance Diet) containing no added antibiotic,
chemotherapeutic or prophylactic agent.
- Water (ad libitum): Tap water
- Acclimation period: At least 6 days before treatment start under laboratory conditions.

Analysis of the batch of diet used and water did not provide evidence of contamination that might have prejudiced the study.

ENVIRONMENTAL CONDITIONS

Air conditioned room kept at positve pressure without re-circulation of the filtered fresh air supplied to the room.
Controlled environmental conditions were set at:
- Air changes per hour in the animal room: controlled periodically
- Temperature (°C): 21 ± 2°C
- Relative Humidity (%): 40 to 70%
- Photoperiod (artificial lighting): 12 hrs day / 12 hrs night
There was no mentioning of any deviations from these ranges, which compromised the integrity or validity of the study.



Vehicle:
acetone/olive oil (4:1 v/v)
Concentration:
Main Study:
0, 5, 10, and 25%

WS405777 was unsuitable for dosing at 50% in any of the vehicles stated in the protocol; 25% was the maximum achievable concentration.
No. of animals per dose:
Main Study:
4 female animals per dose
Details on study design:
Compound Solubility:

WS405777 was unsuitable for dosing at 50% in any of the vehicles stated in the protocol; 25% was the maximum achievable concentration forming a white suspension.

Treatment Preparation and Administration:

On three consecutive days, groups of 4 female mice were treated by topical application to the entire dorsal surface of both ears with 25 μL/ear/day at the following concentrations (w/v) of test substance in the vehicle: 0, 5, 10, and 25%, respectively.

The test substance preparations were prepared freshly on each day of administration.

Observations, Measurements and Endpoints (Pooled treatment group approach):

All animals were checked daily for signs of ill health or toxicity. The ears were also examined daily for signs of irritation. In addition, bodyweights were recorded on Days 1 (prior to treatment) and 6 (prior to termination). On Day 6, all animals were injected into the tail vein 3H-methyl thymidine diluted in phosphate buffered saline at a nominal dose of 20 µCi per mouse, in order to measure lymphocyte proliferation by radioactive labelling. Five hours afterwards the draining (auricular) lymph nodes were excised and pooled for each experimental group. Single cell suspensions were prepared for determination of incorporated radioactivity.

Criteria Used to Consider a Positive Response:

The test substance is regarded as a sensitizer if at least one concentration of the test substance produces a stimulation index (SI) ≥ 3.


Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Statistics:
Data were not statistically analysed.
Positive control results:
A stimulation index (SI) of 8.7 was attained in a contemporaneous positive control assay with the same strain of mice (CBA/Ca) in response to 25% v/v hexyl cinnamic aldehyde in AOO, thus demonstrating the reliability and sensitivity of this test system and assay to detect skin sensitization potential in this laboratory.
Parameter:
SI
Remarks on result:
other: Stimulation Index (SI) values for the experimental groups treated with 5, 10, and 25 % w/v test substance dilutions were 0.9, 1.2, and 1.2, respectively.
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: Overall DPM/lymph node values for the experimental groups treated with 5, 10, and 25% w/v test substance dilutions were 510, 628, and 681 DPM/node, respectively. For the vehicle control group, 546 DPM/node were recorded.

Mortality / clinical signs:

There were no deaths, no signs of ill health or toxicity and no signs of local irritation over the treated area. Greasy fur on the head was noted following each dosing occasion.

Body weight: There was no indication of adverse effects on bodyweight attributable to treatment with the test substance.

As outlined in the „Validity Assessment Report“ for the read-across approach (see IUCLID Section 13) read-across from testing data obtained with the UVCB substance WS405777 is considered appropriate for the safety evaluation as well as classification and labelling of the mono-constituent substance WS406663 based on the close chemical similarity between the two substances.

Interpretation of results:
not sensitising
Remarks:
Migrated information Criteria used for interpretation of results: EU
Executive summary:

As outlined in the „Validity Assessment Report“ for the read-across approach (see IUCLID Section 13) read-across from testing data obtained with the UVCB substance WS405777 is considered appropriate for the safety evaluation as well as classification and labelling of the mono-constituent substance WS406663 based on the close chemical similarity between the two substances.

WS406663 does not necessitate any classifcation regarding skin sensitisation.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:
Justification for selection of skin sensitisation endpoint:
Justification for use of the results obtained with the read-across source substance WS405777 for classification of WS406663 is provided in the “Validity Assessment Report for the read-across approach” attached in IUCLID Section 13.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Based on the low stimulation indices observed in the local lymph node assay, WS405777 is considered not to be a skin sensitizer and does not warrant any classification regarding skin sensitisation according to European classification rules [Regulation (EC) 1272/2008].

The same conclusion of non-classification for skin sensitising properties can be drawn for the read-across target substance WS406663 based on the close chemical similarity between the two substances (see IUCLID Section 13 „Validity Assessment Report“ for the read-across approach).